docs: def download_signed_document(self, signature_id, document_id):
          """
          Get the audit trail of concrete document
          @signature_id: Id of signature
          @document_id: Id of document
          """
          connection = Connection(self.token)
  
          connection.set_url(self.production, self.SIGNS_DOCUMENTS_SIGNED_URL % (signature_id, document_id))
  
          response, headers = connection.file_request()
  
          if headers['content-type'] == 'application/json':
              return response
  
          return response